Thread: Charging issues

Although i possibly not the answer i will post it anyway just to get others perspectives.
The telltale light on my aux battery is showing clear ie charge required, main battery although indicator is green voltage is low.
At rest main batt reads 12.5 and aux 12.2 as measured yesterday afternoon, with engine running voltage at main batt is 14.49 ish so alternator is fine and aux reads 14v at terminals.
To me this would suggest my 2yo main battery is failing which makes the VSR divert charge to main and not aux although while running 14V at aux terminals suggests otherwise ?

Both batteries are the same lead acid type and similar age, not having any starting issues but previously the main would generally rear around just under 13V and aux was similar.
Might check the earthing in case they have corrosion on them.